xamarin - 如何在 xamarin.forms 中的 listview 和 sqlite 数据库之间进行数据绑定？

Question

我尝试使用有关使用本地数据库和阅读工作应用程序（Tasky）源代码的指南来了解如何实现这一点，但我的列表视图仍然是空的。另外我想知道解决这样的问题是否可以，或者我应该创建一个视图模型，其中包含一个可观察的集合，其中填充了从数据库获得的结果？这是我的代码：

这是我的模型：

public class AppUser
{
[PrimaryKey, AutoIncrement]
public long AppUserId { get; set; }

        [MaxLength(255)]
        public string Name { get; set; }
        [MaxLength(255)]
        public string ContactName { get; set; }
        public string Password { get; set; }
        public string MedicalNumber { get; set; }
        public string PoliceNumber { get; set; }
        public string FireNumber { get; set; }
        public string FamilyNumber { get; set; }
        public string CustomTextMessage { get; set; }



    }

这是我的数据访问层

public class AppUserDbConnect
{
static SQLiteAsyncConnection _database;

    public AppUserDbConnect(string dbPath)
    {
        _database = new SQLiteAsyncConnection(dbPath);
        _database.CreateTableAsync<AppUser>().Wait();
    }
    public Task<List<AppUser>> GetItemsAsync()
    {
        return _database.Table<AppUser>().ToListAsync();
    }

    public Task<List<AppUser>> GetItemsNotDoneAsync()
    {
        return _database.QueryAsync<AppUser>("SELECT * FROM [AppUser] WHERE [Done] = 0");
    }

    public Task<AppUser> GetItemAsync(int id)
    {
        return _database.Table<AppUser>().Where(i => i.AppUserId == id).FirstOrDefaultAsync();
    }

    public Task<int> SaveItemAsync(AppUser item)
    {
        if (item.AppUserId != 0)
        {
            return _database.UpdateAsync(item);
        }
        else
        {
            return _database.InsertAsync(item);
        }
    }

    public Task<int> DeleteItemAsync(AppUser item)
    {
        return _database.DeleteAsync(item);
    }
}
}

这是我的看法：

    <StackLayout>
            <Label Text="SETTINGS/MY Numbers" FontSize="30" FontAttributes="Bold"/>
        <ListView x:Name="ListOfNumbers" >

            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <ViewCell.View>
                            <Label Text="{Binding MedicalNumber}" />
                        </ViewCell.View>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>

        </ListView>
    </StackLayout>

</ContentPage>

最后是后面的代码：

[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class MyNumbersPage : ContentPage
{

                    public MyNumbersPage ()

                    {

                        InitializeComponent( );
                         BindingContext = new AppUser();

                    }
                    protected async override void OnAppearing()
                    {
                        base.OnAppearing();
                        ListOfNumbers.ItemsSource = await App.AppUserDatabase.GetItemsAsync();

                    }

}

这是添加联系人页面：

<StackLayout>
            <Picker x:Name="picker" Title="Select a Country Code">
                <Picker.ItemsSource>
                    <x:Array Type="{x:Type x:String}">
                        <x:String>+234</x:String>
                        <x:String>+264</x:String>
                        <x:String>+27</x:String>
                        <x:String>+266</x:String>
                        <x:String>+263</x:String>
                        <x:String>+218</x:String>
                        <x:String>+211</x:String>
                    </x:Array>
                </Picker.ItemsSource>
            </Picker>

            <Entry  Placeholder="Enter the Contact Name" x:Name="Name"/>
            <Entry  Keyboard="Numeric" Placeholder="Enter your Number" x:Name="Number"/>
            <Button Text="Cancel" Clicked="Cancel" />
            <Button Text="Save" Clicked="AddNewContact"/>
        </StackLayout>

还有代码隐藏：

public partial class AddContactForFamily : ContentPage
    {
        public string pickerValue;
        public AddContactForFamily ()
        {
            InitializeComponent ();
        }

        async void AddNewContact(object sender, EventArgs e)
        {
            var picker = (Picker)sender;
            int selectedIndex = picker.SelectedIndex;

            if (selectedIndex != -1)
            {
            pickerValue = (string)picker.ItemsSource[selectedIndex];
            }

            var contact = new AppUser {ContactName = Name.Text, FamilyNumber = pickerValue +Number.Text };
            if (App.AppUserDatabase.SaveItemAsync(contact) != null)
            {
              await  DisplayAlert("Alert", "You have added a contact successful", "OK");
               await Navigation.PopAsync();

            }


        }

        async void Cancel(object sender, EventArgs e)
        {
           await  Navigation.PopAsync();
        }
    }